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The majority of limestone reservoirs in China are characterized by deep burial， low porosity， and low permeability and are influenced by factors such as elevated temperatures， high closure pressures， and strong heterogeneity. Conventional hydrochloric acid fracturing techniques often fail to achieve non-uniform etching on such reservoirs， resulting in poor transformation effects and hindering the efficient development of such reservoirs. The acid fracturing technology of multi-stage alternating injection was used to facilitate non-uniform etching of fracture wall surfaces by iteratively forming viscous fingering in the prepad. However， the law governing the acid-etching fracturing of multi-stage alternating injection remains unclear， and the acid injection stage boundaries are not determined. At present， acid fracturing design typically relies on empirical approaches. To address these gaps， this study built an acid fracturing model of multi-stage alternating injection for limestone reservoirs by considering the influence of viscosity variation and alternating stages based on a two-scale continuous acidification model. Based on the acid fracturing model of multi-stage alternating injection， the influence of acid viscosity， acid injection rate， and acid injection stages on the acid fracture effects was analyzed by combining the acid rock reaction kinetics， acid-etched fracture experimental data， and numerical simulation results. The acid-etching law of multi-stage alternating injection in limestone reservoirs and the acid injection stage boundaries were determined， and the breakthrough volume of acid fluid was introduced to provide the basis for site optimization. The findings suggest that to enhance the non-uniform etching of fracture wall surfaces and obtain high conductivity of acid-etching fractures， an alternating injection process involving hydrochloric acid and thickened acid should be adopted for pure limestone reservoirs at a formation temperature of 90 °C. 0.4% HPAM-thickened acid should be added when the acid injection rate is 5 m3/min， with an optimal acid injection stage of no more than three. At this time， the breakthrough volume of acid fluid is the smallest， which is suitable for on-site construction.

Hydraulic fracturing technology has become a key technical means to improve coalbed methane (CBM) yield. The evolution of CBM reservoir permeability before and after hydraulic fracturing reflects the induced fracturing level. By means of fracturing and stress-permeability experiments on four high rank coal samples of No.3 coal seam of the Permian Shanxi Formation in Sihe Coal Mine, Jincheng Mining Area, Shanxi Province, the permeability changes before and after fracturing are tested, and the evolution of pillar coal sample permeability with stress before and after fracturing is revealed. The results show that under the condition of constant confining pressure and axial pressure, the pore pressure of coal samples increases gradually with the increase of injection pressure. When the injection pressure is greater than the fracture pressure, the coal sample breaks, and the fracture pressure of the coal sample increases linearly with the increase of the confining pressure. Under the same injection pressure, the effective stress increases with the increase of confining pressure and axial pressure. The permeability of coal samples before and after hydraulic fracturing decreases exponentially with the increase of effective stress, and the permeability after fracturing is significantly greater than that before fracturing. The permeability improvement coefficient (PIC) of CBM reservoir is used to evaluate the permeability improvement effect of coal samples. The PIC of four test coal samples increase exponentially with the increase of effective stress, but decrease with the increase of confining pressure. The permeability of CBM reservoir mainly depends on the degree of fracture development and the size of fracture width in coal. The permeability of fractured reservoir is in direct proportion to the 3rd power of fracture width. After hydraulic fracturing, the average fracture length, fracture porosity and fracture width increase by 70.81%−253.25%, 171.88%−383.02% and 20.31%−32.43%, respectively. The fracture width decreases with the increase of effective stress in a negative exponential function. The test results are compared with the measured coal reservoir permeability before and after hydraulic fracturing. The two have good consistency, which explores an effective way for the evaluation of the effect of hydraulic fracturing of coal reservoirs.

In the pursuit of digital transformation, college libraries have increasingly embraced the promotion of digital reading as a critical initiative. While numerous studies have delved into the strategies employed by college libraries in their digital transformation endeavors, there remains a lack of research elucidating the direct influence of digital reading on reader service satisfaction within these institutions. Drawing upon the service quality model, this paper aims to address this gap by examining the multifaceted influence of digital reading on reader service satisfaction in college libraries. By examining the various dimensions of digital reading services, this study employs the fsQCA approach to uncover specific combinations that contribute to heightened levels of reader service satisfaction. The results reveal three distinct configurations that can explain the high level of reader service satisfaction. By elucidating these critical relationships, this research not only provides a contribution to the research regarding the evolving role of college libraries but also provides practical insights for college libraries aspiring to realize digital transformation by promoting digital reading. [ABSTRACT FROM AUTHOR]

Alkylamines form the backbone of countless nitrogen‐containing small molecules possessing desirable biological properties. Despite advances in amine synthesis through transition metal catalysis and photoredox chemistry, multicomponent reactions that leverage inexpensive materials to transform abundant chemical feedstocks into three‐dimensional α‐substituted alkylamines bearing complex substitution patterns remain scarce. Here, we report the design of a catalyst‐free electroreductive manifold that merges amines, carbonyl compounds and carbon‐based radical acceptors under ambient conditions without rigorous exclusion of air and moisture. Key to this aminative carbofunctionalization process is the chemoselective generation of nucleophilic α‐amino radical intermediates that readily couple with electrophilic partners, providing straightforward access to architecturally intricate alkylamines and drug‐like scaffolds which are inaccessible by conventional means. [ABSTRACT FROM AUTHOR]

In response to the issues of premature convergence, lack of population diversity, and poor convergence accuracy in the traditional Sand Cat Swarm Optimization (SCSO) algorithm, a Multi-Strategy Improved SCSO (MISCSO) algorithm is proposed. Firstly, multiple population strategies are used to avoid premature convergence and falling into local optima traps. Secondly, a distribution estimation learning strategy is introduced to represent the relationships between individuals, using probability models to improve algorithm performance. Next, the diversity of candidate solutions in the elite pool is utilized to expand the search space and enhance the algorithm's ability to avoid local solutions. Lastly, a Cauchy disturbance strategy is adopted to accelerate the convergence speed of the algorithm, thereby improving the search efficiency and convergence accuracy. The experimental results of CEC2017 tests show that the improved algorithm balances convergence speed and global search capabilities effectively. Finally, the algorithm is applied to actual drone path planning and compared with six other intelligent algorithms, demonstrating the practicality and effectiveness of the improved algorithm. [ABSTRACT FROM AUTHOR]